1. Technical Field
This invention relates to the art of providing liners for cylinder bores of internal combustion engine blocks, and more particularly to techniques for joining such liners to the cast structure of such blocks.
2. Discussion of the Prior Art
Light alloy cast engine blocks provide an opportunity to achieve significant weight reduction when compared to traditional cast iron engine blocks. However, to provide a compatible wear surface for the pistons operating within such engine blocks, iron cylinder liners are commonly used. These liners are placed within the engine block by being cast-in-place or by being locked by an interference fit. Cast-in-place liners (such as disclosed in U.S. Pat. Nos. 3,521,613 and 4,252,175) add complexity to the casting process and increase the cost and severity of foundry scrap. The interference fit process permits first the casting of blocks without liners and thus reduces the scrap concerns; the liner is inserted subsequently by extensive heating of the blocks to achieve an expansion and then later cooling of the block with the liner in place to achieve the interference fit between the cylinder bore and the liner (see U.S. Pat. No. 3,372,452). This process slows and complicates the manufacture of engines within an engine plant, and, in general, is not suitable for high production volumes typical of major automotive engine plants.
To function properly, the inserted liners must have a full integral surface-to-surface bond that promotes thermal transfer as if the liner and cylinder bore were one unitary piece. This invention has discovered that staking can achieve such integral surface-to-surface bond without the need for heating. Applicants are unaware of any prior art that carries out staking of liners within cylinder bores for engine blocks.
Ball mandrel expansion has been used in the past for sizing of the interior surfaces of a tubular member (see U.S. Pat. Nos. 1,402,508; 1,722,389; and 2,613,431) without regard to any bonding of such tube to another body. Mandrel expansion has also been used to deform pipe shafts to irregular openings in cam lobes for making a camshaft (such as illustrated in U.S. Pat. Nos. 4,293,995; 4,382,390; and 4,597,365). But these disclosures require only that there be some keying to promote rotational drive therebetween and not a full circumferential thermal exchange interface.
Mandrel expansion has also been used to deform lips of cylinder liners, but never with the intent of promoting a full circumferential thermal exchange interface between the liner and a surrounding cylinder bore (see U.S. Pat. Nos. 2,435,837 and 3,372,452).
It is therefore an object of this invention to provide a highly efficient, productive and lower-cost method for joining cylinder liners to cylinder bores without the need for heating, which process provides stronger, more durable liners with thinner gauge metals and with less scrap.